Generally robo-investors do the same thing all the time: The portfolio expects to have these holdings at these target percentages of the portfolio. If one hold

Generally robo-investors do the same thing all the time: The portfolio expects to have these holdings at these target percentages of the portfolio. If one holding is low and another is high (by more than some specific margin) sell a bit of the high one to buy a bit of the low on. This eases your fall in a market where different things are falling at different rates, theoretically.